The present invention relates to a canister used for an evaporative fuel treatment device of a vehicle, and more particularly to a canister having a structure of a series of flow passages which is formed by connecting a plurality of adsorbent chambers together to form a U-turn-shaped flow passage.
As a well-known technique, in a vehicle using an engine, in order to prevent evaporated fuel (or evaporative fuel) in a fuel tank from being released into the atmosphere, an evaporative fuel treatment device having a canister as a main component is provided.
With respect to the canister, an adsorbent such as an activated carbon fills an inside of a casing of the canister. The canister has the function of adsorbing, by the adsorbent, the evaporated fuel generated from the fuel tank in an engine halt state, and desorbing the evaporated fuel from the adsorbent and introducing it into an intake system of the engine by the atmospheric air introduced from an air port (also called a drain port) at engine start-up or in an engine operating state.
Since it is necessary for such canister to secure a sufficient length of a flow passage from a charge port and a purge port, which are provided at one end portion of the canister, to the air port which is provided at the other end portion, i.e. a sufficient length in a flow direction of the adsorbent, a structure in which two or three separate adsorbent chambers are connected in order so as to form a U-turn-shaped flow passage is generally employed, as disclosed in Japanese Patent Provisional Publication No. 2012-007501 (hereinafter is referred to as “JP2012-007501”). In an example shown in FIG. 4 in JP2012-007501, a canister has three adsorbent chambers. A first adsorbent chamber and a second adsorbent chamber, which are positioned at a charge port side, are fixedly connected to each other as one unit by a case, and communicate with each other by a communication passage formed at a part of the case. Then, a third adsorbent chamber is formed by a different case, and one end of the third adsorbent chamber and one end of the second adsorbent chamber are connected together through an external pipe such as flexible rubber tube.
On the other hand, Japanese Patent Provisional Publication No. 2008-106610 (hereinafter is referred to as “JP2008-106610”) discloses a structure in which a baffle plate is provided in an opposing position to the air port in order that the atmospheric air coming from the air port widely diffuses upon purging.